The present invention relates generally to a roller for use in a fixing section or the like of a copying machine, a line printer, facsimile equipment. More specifically, the invention relates to an elastic roller for use in a fixing operation.
Generally, a fixing section of a copying machine or the like is arranged as shown in FIG. 3. Copy paper 13 having toner 12 transferred thereon is passed between a heat-fixing roller 10 and a pressure-fixing roller 11 to fix an image on the copy paper by the double action of heat and pressure.
Heat fixing roller 10 is formed by applying a fluororesin coating 15 of the order of tens of microns to the surface of a roller core 14, made of metal, such as aluminum or the like, ceramics or heat-resisting plastics, or a roller formed by applying a silicone rubber or fluororubber coating having the thickness of 1 mm or less to the surface of the roller core 14.
Pressure fixing roller 11 is formed by applying a heat-resisting rubber coating 17, having a thickness of the order of millimeters and hardness of the order of tens of degrees, to a roller core 16 made of aluminum or the like.
Separating pawls 18, each having a width of the order of millimeters, are attached at four or five places to prevent the copy paper from coiling, usually on the heat-fixing roller side. In high-speed copying machines and double-side copying machines, separating pawls 19 are also provided on the pressure-fixing roller side as shown in FIG. 3. Reference numeral 20 designates a heater.
However, the fixing rollers 11 and 15 are sometimes damaged by being scraped by the separating pawls when the copy paper is coiled on the rubber roller, so that the rubber roller cannot be used any more. In order to overcome this problem, there was developed a roller as disclosed in Japanese Patent Unexamined Publication No. 60-179770.
The roller disclosed in Unexamined Publication 60-179770 is formed by covering a roller core with a porous (poly-)tetrafluoroethylene resin (P.T.F.E.), impregnating the porous portions of the porous P.T.F.E. with heat-resistant liquid silicone rubber, and hardening the liquid silicone rubber. The rubber is hardly damaged by the separating pawls and that the lifetime thereof is prolonged several times.
However, the roller disclosed in Unexamined Publication No. 60-179770 has deficiencies in that, even if the silicon rubber bonds to the roller core due to a high self-adhesive property, sufficiently large bonding strength is not attained because of occurrence of separation of the porous (poly-)tetrafluoroethylene resin from the rubber at the interference therebetween. This is one of factors which contributes to poor durability of the roller. The disclosed roller also has the disadvantage in that the bonding strength is weakened in long-term use.
Further disadvantages of such a fluororesine coating roller include poor quality of the copied image, difficulty in fixing, and tendency to wrinkle the paper etc., because the roller has no elesticity.
Thus, an object of the present invention is to solve the aforementioned problems.